Saturday, the last day of registration for presidential hopefuls in Iran, did not lack for twists and surprises. The two leading members of the 2+1 coalition, Tehran Mayor Mohammad Bagher Qalibaf and former Foreign Minister Ali Akbar Velayati, finally signed up, as did chief nuclear negotiator Saeed Jalili. At the very last minute, ex-President Akbar Hashemi Rafsanjani and former chief of staff Esfandiar Rahim Mashaei also showed up to register as candidates.

The situation is that there are now figures from across the political spectrum in the fray. The 2+1 coalition, which also features former parliament Speaker Gholam-Ali Haddad Adel, is widely seen as enjoying the backing of Iran's supreme leader, Ayatollah Ali Khamenei. There is a separate so-called ‘principlist’ coalition led by former Foreign Minister Manouchehr Mottaki. Moreover, several members of the camp of President Mahmoud Ahmadinejad, chief among them his right-hand man Mashaei, have registered. Lastly, in addition to the centrists/reformists, led by Rafsanjani, there are some independent figures.

In other words, after years of increasingly factional infighting, all the ingredients for a vicious campaign season are at hand.

There are two filters which will likely act to stabilize the playing field for the June 14 election.